update idletasks
    regsub -all [file join {} non_existent] $x "non_existent"
} -cleanup {
    rename bgerror {}
} -result {{{a simple error} {a simple error
    while executing
"error "a simple error""
    ("after" script)} NONE} {{couldn't open "non_existent": no such file or directory} {couldn't open "non_existent": no such file or directory
    ("after" script)} NONE} {{couldn't open "non_existent": No such file or directory} {couldn't open "non_existent": No such file or directory
    while executing
"open non_existent"
    ("after" script)} {POSIX ENOENT {no such file or directory}}}}
    ("after" script)} {POSIX ENOENT {No such file or directory}}}}
test event-5.2 {Tcl_BackgroundError, HandleBgErrors procedures} -setup {
    catch {rename bgerror {}}
} -body {
    proc bgerror msg {
	global x
	lappend x $msg
	return -code break